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Old December 5, 2012, 10:12 AM   #10
Unclenick
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Join Date: March 4, 2005
Location: Ohio
Posts: 21,017
Kilotanker22,

You can look at my list of pressure signs. All brass is not equal, and you can often get pressure signs earlier in some brands than in others, which is why it's a good habit to knock a load down 5% and work back up when you change a component make or lot number. These days I usually use 6%, then increment in 2% steps when checking pressure. That way it's just 4 rounds to land back where I was.

Some powders have temperature compensation and some don't. Denton Bramwell found barrel temperature to be a bigger factor than powder temperature in his tests. So how you allow for temperature isn't simple to work out. It's both the powder and your rate of fire and how long rounds have to sit in a hot chamber that this will all depend on.

An old rule of thumb is to assume pressure will change about 1% for every ten degrees Fahrenheit, but that assumes each shot is from a cold barrel. Given the variables, therefore, you do best to develop loads and try them in your worst case warm barrel conditions for the kinds of rates of fire you actually use.
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